Informatization is an important feature of smart grid. With the construction of smart grid and the constant depth development of electric power information, the information networks of electric power have been continued to invade by all kinds of network threats. Traditional information security protection system for electric power had been unable to meet the security threats demand of ever changing and growing. Moreover, the cost of electrical safe operation was increased. Meanwhile, with the further application of electric power information engineering, operation capacity of electric power is required to be fully improved so that safe and stable operation is essential to electric power information system. Cloud security is service form that cloud computing provides for users. In view of the advantages of cloud computing and cloud security, architecture of electric power information security protection based on cloud security (AEPISP-CS) is put forward which combines with the current power information security status. Meanwhile, anti-virus system, spam mail filtering, threat detection based on cloud security are described in detail.